US 7936729 B2 Abstract The invention discloses a distribution method of channelization code in code division multiple access system, which including: A. the spread spectrum codes distributed to every sector and the correlated coefficients between the spread spectrum codes distributed to every neighboring sector are calculated according to the cellular codes and the channelization codes distributed to every sector, when the network is programmed; B. every sector is divided into different regions and the edge region of every sector is formed; C. the priority of which every channelization code is at the edge region of every sector is decided according to the correlated coefficients between the spread spectrum codes distributed to every neighboring sector; D. the position information of user is real-time calculated during the operation of system, and which region the user positioned in sector is determined according to the position information; E. according to the region at which the user positioned and the decided priority of which every channelization code is at the edge region of every sector, distribute the channelization codes to every user. The method of the invention can reduce the same-frequency interference of the edge region of sector due to the correlation of the spread spectrum codes, so as to improve the communication quality of which the users are at the edge regions of the sectors.
Claims(11) 1. A method for allocating channelization codes in a CDMA (Code Division Multiple Access) system, comprising:
A. computing spread spectrum codes allocable in each sector according to a cellization code and a channelization code that are allocated to each sector during the network planning of a CDMA system, computing the correlativity between spread spectrum codes of adjacent sectors, and obtaining a correlation coefficient between the spread spectrum codes allocable in each pair of adjacent sectors;
B. performing region division on each sector, and marking out the edge region of each sector;
C. determining a priority of each channelization code corresponding to the spread spectrum code of each adjacent sector in the edge region of each sector, according to the correlation coefficient between the spread spectrum codes allocable in each pair of adjacent sectors;
D. computing a location information of a user by the system in real time during the operation of the CDMA system, and determining to which region of the sector the user pertains according to the location information; and
E. allocating a channelization code to each user by the system according to the region to which each user pertains and the priority of each channelization code in the edge region of each sector determined in step C.
2. The method for allocating channelization codes according to
obtaining the spread spectrum code allocable in each sector by bit-multiplying the allocated scrambling code of each sector with all the allocable channelization codes.
3. The method for allocating channelization codes according to
wherein, ρ
^{(l} ^{ 1 } ^{,l} ^{ 2 } ^{,q} ^{ 1 } ^{,q} ^{ 2 } ^{) }is the correlation coefficient; L is the number of system sectors; Q is the number of channelization codes; S^{(l} ^{ 1 } ^{,q} ^{ 1) }(m) is the spread spectrum code allocable in one of the two adjacent sectors; S^{(l} ^{ 2 } ^{,q} ^{ 2) }(m) is the spread spectrum code allocable in the other of the two adjacent sectors.4. The method for allocating channelization codes according to
setting an edge angle threshold, wherein the region that deviates from the sector center in the left in excess of the angle threshold is referred to as the left edge region of the sector; and the region that deviates from the sector center in the right in excess of the angle threshold is referred to as the right edge region of the sector.
5. The method for allocating channelization codes according to
receiving an arrival wave signal sent by a user via the system and computing the power angular spectrum of the arrival wave signal, wherein the angle on which the maximum power of the arrival wave signal exists is the location information of the user; and
the method of determining to which region of the sector the user pertains in step D is as follows: determining whether the angle on which the maximum power of the arrival wave signal exists is in a region that deviates from the sector center in the left in excess of an angle threshold, or in a region that deviates from the sector center in the right in excess of an angle threshold; if yes, then the user is in the left edge region or the right edge region of the sector; otherwise, the user is in the center region of the sector.
6. The method for allocating channelization codes according to
the step D further comprises the step of sequencing the users from far to near according to the distances of the users from the sector center; and
in the step E, the system allocates a channelization code to each user one by one according to the sequence of the users.
7. The method for allocating channelization codes according to
the step A further comprises the step of recording the obtained correlation coefficients between the spread spectrum codes allocable in each pair of adjacent sectors in a correlation coefficient table of the spread spectrum codes in the adjacent sector;
the method of determining the priority of each channelization code in the edge region of each sector in step C is as follows:
selecting channelization codes corresponding to a set of spread spectrum codes with small correlation coefficient from the correlation coefficient table of the spread spectrum codes in the adjacent sectors, and setting the priority thereof as high priority; and setting the priority of the channelization codes corresponding to a set of spread spectrum codes with large correlation coefficient as low priority.
8. The method for allocating channelization codes according to
setting the priority of a same channelization code as different in the two edge regions of the same sector; and in the edge regions of one sector, if some channelization codes are set as high priority, then the rest channelization codes will be set as low priority.
9. The method for allocating channelization codes according to
C1. selecting two adjacent sectors from all of the sectors, and determining the adjacent edge regions of the two sectors;
C2. selecting channelization codes corresponding to a set of spread spectrum codes with small correlation coefficient from the correlation coefficient table of the spread spectrum codes in the two adjacent sectors, and setting the priorities of these channelization codes in the adjacent edge regions of the two sectors as high priority; and setting the priorities of these channelization codes in non-adjacent edge regions of the two sectors as low priority, according to the principle that the same channelization code has a high priority only in one edge region of a sector and has a low priority in the other edge region of the same sector;
C3. selecting channelization codes corresponding to a set of spread spectrum codes with large correlation coefficient from the correlation coefficient table of the spread spectrum codes in the two adjacent sectors, and setting the priorities of these channelization codes in the adjacent edge regions of the two sectors as low priority; and setting the priorities of these channelization codes in the non-adjacent edge regions of the two sectors as high priority, according to the principle that the same channelization code has a high priority only in one edge region of a sector and has a low priority in the other edge region of the same sector;
C4. selecting a sector adjacent to one of the above sectors of which the priority has been set, and determining the edge region of the selected sector, which is adjacent to the sector of which the priority has been set;
C5. according to the correlation coefficient table of the spread spectrum codes in the selected sector and the sector of which the priority has been set, and the channelization codes with high priority in the edge region in the sector of which the priority has been set, determining the channelization codes of the selected sector corresponding to the spread spectrum codes having small correlation coefficient with the spread spectrum codes corresponding to the channelization codes with high priority; setting the priorities of these channelization codes in the adjacent edge regions of the selected sector and the sector of which the priority has been set as high priority, and setting the priorities of these channelization codes in the non-adjacent edge regions of the selected sector and the sector of which the priority has been set as low priority, according to the principle that the channelization codes only have a high priority in one edge region of the sector;
C6. selecting the channelization codes corresponding to a set of spread spectrum codes with large correlation coefficient and the priority of which is not determined in step C5 from the correlation coefficient table of the spread spectrum codes in the two adjacent sectors, according to the correlation coefficient table of the spread spectrum codes in the selected sector and the sector of which the priority has been set, and setting the priorities of these channelization codes as low priority; and setting the priorities of these channelization codes in the non-adjacent edge regions of the selected sector and the sector of which the priority has been set as high priority, according to the principle that the channelization codes only have a low priority in one edge region of the sector; and
C7. repeating steps C4 to C6 if there are sectors of which the priorities are not set, until the priorities of all the sectors are set.
10. The method for allocating channelization codes according to
the step C further comprises: for the spread spectrum codes of the current sector having large correlation coefficient with the spread spectrum codes used in a common channel in adjacent sectors for sending omnidirectionally, the priorities thereof in the corresponding edge regions are set as low priority; and
the step E further comprises: allocating the channelization codes corresponding to the spread spectrum codes used in the common channel according to the priority of each channelization code in the edge region of each sector.
11. The method for allocating channelization codes according to
allocating channelization code by the system to the user in an edge region according to the priority of each channelization code in the edge region of each sector determined in step C; and allocating channelization code to the user outside the edge region at random or according to the serial number of the channelization code.
Description This application is related to, and claims priority from, Patent Cooperation Treaty (PCT) Patent Application Ser. No. PCT/CN2005/002105, filed Dec. 7, 2005, which in turn draws priority from Chinese Patent Application Ser. No. 200410097009.5, filed Dec. 8, 2004, the entire contents of each of which is incorporated herein by reference. The present invention relates to a method for allocating code words in a CDMA (Code Division Multiple Access) system, in particular, to a method for allocating channelization codes in a CDMA system. At present, the channelization codes in a CDMA system are usually allocated at random or in turn during channel allocation. For example, in a multi-sector Time Slot CDMA system employing smart antennas, the channelization codes are allocated at random or according to the sequence number of the channelization codes during channel allocation. The CDMA code resources in a multi-sector Time Slot CDMA system with smart antennas are shown in 1. Measuring the interference power or related physical quantities of each time slot in real time. 2. Allocating a user to an optimum one of the 1 to N time slots, for example, the time slot with the minimum interference power. 3. Which channelization code of the optimum time slot occupied by the user is used at random or in turn, for example, in the order of serial number of the channelization codes from small to large: 1, 2, . . . , Q. After the channelization code is determined, the spread spectrum code of the channel is obtained by calculating the dot product of the cellization code (usually it is scrambling code) allocated during system planning and the occupied channelization code. The spread spectrum code is used for distinguishing between different channels in the same cell, and it is sent to a user along with the signaling or data. Scrambling code can change the orthogonal property of a channelization code. Since there are only 16 channelization codes in a multi-sector Time Slot CDMA system with smart antennas, strong correlativity may exist between the different spread spectrum codes of adjacent sectors, or even identical spread spectrum codes may appear. Thus, strong same-frequency interference may be introduced. For a multi-sector system, the radio channel from a user to an adjacent sector is almost the same. As a result, the correlativity of spread spectrum codes will increase the system interference greatly. Moreover, for a system employing short spread spectrum codes, coincident spread spectrum codes may appear. In such a case, the sector edge may cause the demodulation of two users having a coincident code to fail. Therefore, the main object of the present invention is to provide a method for allocating channelization codes in a CDMA system, so that same-frequency interference on the sector edge may be lowered. To attain the above object, following technical solutions are provided according to the embodiments of the invention: A method for allocating channelization codes in a CDMA system, including: A. computing spread spectrum code allocable in each sector according to a cellization code and a channelization code that are allocated to each sector during the network planning of a CDMA system, computing the correlativity between spread spectrum codes of adjacent sectors, and obtaining a correlation coefficient between the spread spectrum codes allocable in each pair of adjacent sectors; B. performing region division on each sector, and marking out the edge region of each sector; C. determining the priority of each channelization code corresponding to the spread spectrum code of each adjacent sector in the edge region of each sector, according to the correlation coefficient between the spread spectrum codes allocable in each pair of adjacent sectors; D. computing the location information of a user by the system in real time during the operation of the CDMA system, and determining to which region of the sector the user pertains according to the location information; and E. allocating a channelization code to each user by the system according to the region to which each user pertains and the priority of each channelization code in the edge region of each sector determined in step C. Wherein, the cellization code is a scrambling code; and computing spread spectrum code allocable in each sector in step A is as follows: obtaining the spread spectrum code allocable in each sector by bit-multiplying the allocated scrambling code of each sector with all the allocable channelization codes. Computing the correlativity between spread spectrum codes of adjacent sectors, and obtaining a correlation coefficient between the spread spectrum codes allocable in each pair of adjacent sectors in step A is as follows:
Wherein, ρ The method of performing region division on each sector in step B is as follows: setting an edge angle threshold, wherein the region that deviates from the sector center in the left in excess of the angle threshold is referred to as the left edge region of the sector; and the region that deviates from the sector center in the right in excess of the angle threshold is referred to as the right edge region of the sector. The step A further comprises the step of recording the obtained correlation coefficients between the spread spectrum codes allocable in each pair of adjacent sectors in a correlation coefficient table of the spread spectrum codes in the adjacent sector; The method of determining the priority of each channelization code in the edge region of each sector in step C is as follows: selecting channelization codes corresponding to a set of spread spectrum codes with small correlation coefficient from the correlation coefficient table of the spread spectrum codes in the adjacent sectors, and setting the priority thereof as high priority; and setting the priority of the channelization codes corresponding to a set of spread spectrum codes with large correlation coefficient as low priority. The method of determining the priority of each channelization code in the edge region of each sector in step C may further comprise: setting the priority of a same channelization code as different in the two edge regions of the same sector; and in the edge regions of one sector, if some channelization codes are set as high priority, then the rest channelization codes will be set as low priority. The process of determining the priority of each channelization code in the edge region of each sector in step C may comprise: C1. selecting two adjacent sectors from all of the sectors, and determining the adjacent edge regions of the two sectors; C2. selecting channelization codes corresponding to a set of spread spectrum codes with small correlation coefficient from the correlation coefficient table of the spread spectrum codes in the two adjacent sectors, and setting the priorities of these channelization codes in the adjacent edge regions of the two sectors as high priority; and setting the priorities of these channelization codes in non-adjacent edge regions of the two sectors as low priority, according to the principle that the same channelization code has a high priority only in one edge region of a sector and has a low priority in the other edge region of the same sector; C3. selecting channelization codes corresponding to a set of spread spectrum codes with large correlation coefficient from the correlation coefficient table of the spread spectrum codes in the two adjacent sectors, and setting the priorities of these channelization codes in the adjacent edge regions of the two sectors as low priority; and setting the priorities of these channelization codes in the non-adjacent edge regions of the two sectors as high priority, according to the principle that the same channelization code has a high priority only in one edge region of a sector and has a low priority in the other edge region of the same sector; C4. selecting a sector adjacent to one of the above sectors of which the priority has been set, and determining the edge region of the selected sector, which is adjacent to the sector of which the priority has been set; C5. according to the correlation coefficient table of the spread spectrum codes in the selected sector and the sector of which the priority has been set, and the channelization codes with high priority in the edge region in the sector of which the priority has been set, determining the channelization codes of the selected sector corresponding to the spread spectrum codes having small correlation coefficient with the spread spectrum codes corresponding to the channelization codes with high priority; setting the priorities of these channelization codes in the adjacent edge regions of the selected sector and the sector of which the priority has been set as high priority, and setting the priorities of these channelization codes in the non-adjacent edge regions of the selected sector and the sector of which the priority has been set as low priority, according to the principle that the channelization codes only have a high priority in one edge region of the sector; C6. selecting the channelization codes corresponding to a set of spread spectrum codes with large correlation coefficient and the priority of which is not determined in step C5 from the correlation coefficient table of the spread spectrum codes in the two adjacent sectors, according to the correlation coefficient table of the spread spectrum codes in the selected sector and the sector of which the priority has been set, and setting the priorities of these channelization codes as low priority; and setting the priorities of these channelization codes in the non-adjacent edge regions of the selected sector and the sector of which the priority has been set as high priority, according to the principle that the channelization codes only have a low priority in one edge region of the sector; and C7. repeating steps C4 to C6 if there are sectors of which the priorities are not set, until the priorities of all the sectors are set. The step C may further comprise: for the spread spectrum codes of the current sector having large correlation coefficient with the spread spectrum codes used in a common channel in adjacent sectors for sending omnidirectionally, the priorities thereof in the corresponding edge regions are set as low priority; The step E further comprises: allocating the channelization codes corresponding to the spread spectrum codes used in the common channel according to the priority of each channelization code in the edge region of each sector. The method of computing the location information of a user by the system in real time in step D may be as follows: receiving an arrival wave signal sent by a user via the system and computing the power angular spectrum of the arrival wave signal, wherein the angle on which the maximum power of the arrival wave signal exists is the location information of the user; The method of determining to which region of the sector the user pertains in step D is as follows: determining whether the angle on which the maximum power of the arrival wave signal exists is in a region that deviates from the sector center in the left in excess of an angle threshold, or in a region that deviates from the sector center in the right in excess of an angle threshold; if yes, then the user is in the left edge region or the right edge region of the sector; otherwise, the user is in the center region of the sector. The power angular spectrum can be Bartlett-direction power spectrum. The step D may further comprise: sequencing the users from far to near according to the distances of the users from the sector center; In the step E, the system allocates channelization code to each user one by one according to the sequence of the users. Specifically, the step E may comprise: allocating channelization code by the system to the user in an edge region according to the priority of each channelization code in the edge region of each sector determined in step C; and allocating channelization code to the user outside the edge region at random or according to the serial number of the channelization code. It can be seen from above technical solutions that by using the method for allocating channelization codes in a CDMA system according to the invention, during network planning, the correlativity between the spread spectrum codes allocable in each sector may be computed according to each channelization code and the cellization code allocated to each sector, the sector region may be divided, and the priority of the channelization code in the edge region of each sector may be determined; and during channel allocation, a channelization code may be allocated to a user according to the region in which the user exists and the priority of the channelization code. The channelization code of the user is allocated according to the priority of the channelization code, and the priority table of the channelization codes is determined according to the correlation coefficient table of the spread spectrum codes of two adjacent sectors, wherein a set of corresponding channelization codes with small correlation coefficient are selected to be set with high priority, and a set of corresponding channelization codes with large correlation coefficient are selected to be set with low priority. Therefore, by allocating channelization codes according to the above method, it can be ensured that the correlation coefficient between the spread spectrum codes generated with the channelization codes allocated according to users in adjacent edge regions of the adjacent cells is small, so that it can be ensured that the spread spectrum code interference of users in adjacent edge regions of the adjacent cells is small, and the communication quality of users can be improved. To make the objects, technical solutions and advantages of the invention more apparent, the invention will now be further illustrated in detail in conjunction with the drawings and embodiments hereinafter. In a method for allocating channelization codes in a CDMA system according to the embodiments of the invention, the correlativity between the spread spectrum codes allocable in each sector is computed according to each channelization code and the cellization code allocated to each sector during network planning, the sector region is divided, and the priority of the channelization code in the edge region of each sector is determined, and a channelization code is allocated to a user according to the region in which the user exists and the priority of the channelization code during channel allocation. The invention will now be illustrated in detail by taking an embodiment in which channelization codes are allocated for a three-sector system as an example. The three-sector system of this embodiment first allocates a cellization code to each sector during network planning. In this embodiment, the cellization code is scrambling code. Referring to After the scrambling codes are allocated, 16 channelization codes and the scrambling code of each cell are computed respectively, and an optional spread spectrum code for each cell is obtained. The computing method is as follows: It is hypothesized that the channelization code is c The correlation coefficient of the spread spectrum code is:
Wherein, ρ For given l
According to this matrix, correlation coefficient tables among the three sectors of the system shown in Table 2-1 is the correlation coefficient table of spread spectrum codes corresponding to sector
Table 2-2 is the correlation coefficient table of the spread spectrum codes corresponding to sector
Table 2-3 is the correlation coefficient table of the spread spectrum codes corresponding to sector
During system planning, the sector regions are also divided, and the priority of the channelization code in the edge region of each sector is determined. In this embodiment, each sector is divided into three regions. Referring to The dividing method is as follows: the region that deviates from the sector center in the left in an angle larger than a certain threshold angle is referred to as left sector edge region; the region that deviates from the sector center in the right in an angle larger than the threshold angle is referred to as right sector edge region; and the central sector region is a region within the threshold angle. In this embodiment, the threshold angle φ Thus, the priority of the channelization code in the edge region of each sector can be determined according to the sector region and the above correlation coefficient tables of the spread spectrum codes between the sectors. There are 3 points in the principle for determining the priority of the channelization code: 1. For some spread spectrum codes with small correlation coefficient in two adjacent sectors, the priorities of the channelization codes corresponding to these spread spectrum codes are set as high priority 1 in the adjacent edge regions of the two cells. 2. For some spread spectrum codes with large correlation coefficient in two adjacent sectors, the priorities of the channelization codes corresponding to these spread spectrum codes are set as low priority −1 in the adjacent edge regions of the two sectors. 3. For some spread spectrum codes of the current sector which have large correlation coefficient with the spread spectrum codes used in a common channel in the adjacent sectors for transmitting omnidirectionally, the priorities of the channelization codes corresponding to these spread spectrum codes are set as low priority −1 in the adjacent edge regions of the two sectors. Here, the spread spectrum codes of the current sector may be spread spectrum codes used in the common channel, or user spread spectrum codes. The generation and allocation of the spread spectrum codes used in the common channel are the same as those of the user spread spectrum codes, except that the sending modes are different: the spread spectrum codes used in the common channel are sent to all the regions of the sector, i.e., sent omnidirectionally; while the spread spectrum codes used by a user is sent to the user according to the location of the user in the sector, but not omnidirectionally. In practical application, the process for determining the priority of each channelization code in the edge region of each sector may comprise: C1. selecting two adjacent sectors from all of the sectors, and determining the adjacent edge regions of the two sectors; C2. selecting channelization codes corresponding to a set of spread spectrum codes with small correlation coefficient from the correlation coefficient table of the spread spectrum codes in the two adjacent sectors, and setting the priorities of these channelization codes in the adjacent edge regions of the two sectors as high priority; and setting the priorities of these channelization codes in non-adjacent edge regions of the two sectors as low priority, according to the principle that the channelization code has a high priority only in one edge region of a sector; C3. selecting channelization codes corresponding to a set of spread spectrum codes with large correlation coefficient from the correlation coefficient table of the spread spectrum codes in the two adjacent sectors, and setting the priorities of these channelization codes in the adjacent edge regions of the two sectors as low priority; and setting the priorities of these channelization codes in the non-adjacent edge regions of the two sectors as high priority, according to the principle that the channelization code has a high priority only in one edge region of a sector; C4. selecting a sector adjacent to one of the above sectors of which the priority has been set, and determining the edge region of the selected sector, which is adjacent to the sector of which the priority has been set; C5. according to the correlation coefficient table of the spread spectrum codes in the selected sector and the sector of which the priority has been set, and the channelization codes with high priority in the edge region in the sector of which the priority has been set, determining the channelization codes of the selected sector corresponding to the spread spectrum codes having small correlation coefficient with the spread spectrum codes corresponding to the channelization codes with high priority; setting the priorities of these channelization codes in the adjacent edge regions of the selected sector and the sector of which the priority has been set as high priority, and setting the priorities of these channelization codes in the non-adjacent edge regions of the selected sector and the sector of which the priority has been set as low priority, according to the principle that the channelization codes only have a high priority in one edge region of the sector; C6. selecting the channelization codes corresponding to a set of spread spectrum codes with large correlation coefficient and the priority of which is not determined in step C5 from the correlation coefficient table of the spread spectrum codes in the two adjacent sectors, according to the correlation coefficient table of the spread spectrum codes in the selected sector and the sector of which the priority has been set, and setting the priorities of these channelization codes as low priority; and setting the priorities of these channelization codes in the non-adjacent edge regions of the selected sector and the sector of which the priority has been set as high priority, according to the principle that the channelization codes only have a low priority in one edge region of the sector; and C7. repeating steps C4 to C6 if there are sectors of which the priorities are not set, until the priorities of all the sectors are set. In this embodiment, the priorities of the sector edge regions are recorded in a channelization code priority table. Specifically, the channelization code priority table is generated in the following steps; and in practical application, the method for generating a priority table may vary as required: Step 1: performing the above steps C1 to C3 at first, so that the priority of each channelization code in the adjacent edge regions of sector The degree of small correlation coefficient will be determined according to practical situations. In this embodiment, the priority of the channelization codes corresponding to the spread spectrum codes with a correlation coefficient of 0 selected by the adjacent sector in the adjacent edge regions is 1. It can be seen from Table 2-1 that there are two groups of channelization codes corresponding to the spread spectrum codes with small correlation coefficient between sector In this embodiment, the first group of the channelization codes corresponding to the spread spectrum codes with small correlation coefficient in sector In the same sector, the following principle may be employed to determine the priority of the same channelization code in different regions: If some channelization codes have high priorities in one edge region, then the priorities of these channelization codes in the other edge region will be low. Thus, in sector There exists another principle: if some channelization codes have high priorities in one edge region, then the priorities of the rest channelization codes in the edge region will be low. For example, if the priorities of channelization codes In sector In sector Step 2: Performing the above steps C4-C6, and setting the priorities of the channelization codes selected for the two edge regions of sector In this embodiment, there are two methods for determining the priorities of the 16 channelization codes in the two edge regions of sector The first method: setting according to the correlation coefficient table of spread spectrum codes in sectors In this embodiment, since the priorities of channelization codes The second method: setting according to the correlation coefficient table of spread spectrum codes in sectors In this embodiment, since the priorities of channelization codes Since there are only three sectors in the system of this embodiment, the above step C7 does not need to be performed. If the system has more than three sectors, then repeat steps C4 to C6 until the priorities of all the sectors are set. According to the above method, the priority table of channelization codes shown in Table 3 may be obtained in this embodiment. The priorities in this embodiment are shown as in Table 3.
In practice, all of the correlation coefficients may be the same. In such a case, the priorities are 0. Additionally, for the channelization codes with high priority selected in a certain region, if the spread spectrum codes corresponding to the channelization codes have large correlation coefficient with the spread spectrum codes in a common channel for omnidirectionally transmitting in the corresponding adjacent sectors, the priorities of these channelization codes are set as −1. In the present embodiment, the priorities of the adjacent edge regions in sector Therefore, a channelization code can be allocated to a user according to the region in which the user exists and the priority of the channelization code during channel allocation. The allocating process is show in Step Step The system computes the power angular spectrum of the arrival wave signal, wherein the angle on which the maximum power of the arrival wave signal exists is the DOA of the user, i.e., the location information of the user. The DOA may be the angle on which the maximum value of the arrival wave signal exists in Bartlett-direction power spectrum. For example, the Bartlett-direction power spectrum of the k
Wherein, a(φ) is the array response vector in direction φ of an antenna array, R Thus, the DOA of the k The above method for estimating DOA is referred to as Bartlett spectrum estimation method in the prior art. In practice, the DOA estimation methods concerned in the invention are not limited to Bartlett spectrum estimation method; other methods that can estimate the DOA are all applicable for the invention. Step Step Step First of all, a positive edge threshold φ
Referring to Step Step Step Step In the present embodiment, it is hypothesized that there are 8 users in each sector currently, and each user occupies 1 code channel. The angle of each user is shown as in Table 4.
It can be known from φ Thus, the allocation result is shown as in Table 5.
In Table 5, since the channelization code of a user is allocated according to the priority of the channelization code, and the priority table of the channelization codes is determined according to the correlation coefficient table of the spread spectrum codes of two adjacent sectors, wherein the channelization codes of two adjacent sectors whose corresponding spread spectrum codes have small correlation coefficient are set to have high priority and the channelization codes whose corresponding spread spectrum codes have large correlation coefficient are set to have low priority. By allocating channelization codes according to the above method, it can be ensured that the correlation coefficient between the spread spectrum codes generated according to the channelization codes allocated to users in adjacent edge regions of the adjacent cells is small, so that it can be ensured that the spread spectrum code interference of users in adjacent edge regions of the adjacent cells is small. For example, in Table 5, the arrival wave angles of users Additionally, in the present embodiment, the channelization codes corresponding to the spread spectrum codes used in the common channel may be further allocated during channelization code allocation according to the priority of each channelization code in the edge region of each sector. In the present embodiment, the location of a user is determined by receiving an arrival wave signal from the user and computing the DOA of the user, wherein DOA is a kind of user location information. In practical application, the sector region in which a user exists may be determined with other location information. It can be seen from the above embodiments that in the method for allocating channelization codes in a CDMA system according to the invention, same-frequency interference at the sector edge caused by the correlativity of spread spectrum codes can be lowered, and the communication quality of a user at the sector edge can be improved. Patent Citations
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